You'll need something at least a couple generations old with an unlockable bootloader. You can run Halium and UB Touch.
It's an Android kernel with a linux VM, but most things work, and it is absolutely private.
Daily Driver real Linux is a couple of years off, probably. They're just getting drivers starting to work now and battery life is a long long way off.
I'm currently trying to figure out some kind of handheld Linux that operates reasonably well and carry a stand alone hotspot. I've even been pondering, throwing a Raspberry Pi compute module onto a 7in screen, but perf is still kinda dicey and power is still a serious issue.